Compositions for imparting water resistance to gypsum wallboards

Abstract

Compositions comprising Kraft lignin and a wax are provided for use as an additive for imparting water resistance to gypsum wallboards. The compositions comprise emulsions of the lignin and wax components or an aqueous dispersion of the wax in a lignin solution. Methods of preparing and using such compositions are also provided.

1 . A composition for use as an additive in the manufacture of gypsum wallboards for imparting water resistance to the manufactured gypsum wallboard, said composition comprising:
 a) an aqueous emulsion of Kraft lignin, wax, water, and a base, wherein:
 the wax is in a molten state; 
 the base is present in an amount sufficient to solubilize the Kraft lignin; and, 
 the weight ratio of Kraft lignin to wax, α, is at least about 0.25; 
   
       or
 b) an aqueous dispersion comprising a Kraft lignin, wax, water, and a base, wherein:
 the wax forms the solid phase; 
 the base is present in an amount sufficient to solubilize the Kraft lignin; and, 
 the weight ratio of Kraft lignin to wax, α, is from about 0.09 to about 2.25. 
 
 
     
     
         2 . The composition of  claim 1 , wherein, for composition (a), the Kraft lignin is present in an amount of at least about 0.20 w/w % relative to gypsum and the wax is present in an amount of at least about 0.20 w/w % relative to gypsum. 
     
     
         3 . The composition of  claim 1 , wherein the weight ratio of the base to lignin, β, is: at least about 0.10; in the range from about 0.1 to about 0.2; or is 0.13. 
     
     
         4 . The composition of  claim 1 , wherein α is: at least about 0.50; or in the range from about 1.0 to about 2.0. 
     
     
         5 . The composition of  claim 1 , wherein the wax is: a petroleum derived slack wax, scale wax, or a refined wax; a synthetic wax; or a natural wax. 
     
     
         6 . The composition of  claim 5 , wherein the wax is a paraffin wax or a refined paraffin wax. 
     
     
         7 . The composition of  claim 5 , wherein the synthetic wax is an alphaolefin wax or a Fischer Tropsch wax. 
     
     
         8 . The composition of  claim 1 , wherein the wax further includes at least one functionalized wax, wherein the functionalized wax is a crude or refined Montan wax, an olefinic succinic anhydride wax, an oxidized polyethylene wax, or an oxidized polypropylene wax. 
     
     
         9 . The composition of  claim 1 , wherein the Kraft lignin is purified Kraft lignin. 
     
     
         10 . The composition of  claim 1 , wherein the Kraft lignin is derived from a LignoBoost™ process, a LignoForce™ process, or another purification process. 
     
     
         11 . The composition of  claim 1 , wherein the base is at least one of sodium hydroxide, potassium hydroxide, and monoethanolamine. 
     
     
         12 . A method of use of the composition of  claim 1  in the manufacture of a gypsum wallboard, the method comprising:
 mixing the composition into a gypsum slurry; and 
 forming the wallboard. 
 
     
     
         13 . A method of preparing the composition of  claim 1  comprising:
 i) for composition (a):
 combining an aqueous solution comprising the Kraft lignin and the base with the molten wax; and 
 emulsifying the mixture of the lignin and base solution and the molten wax under high shear to form an emulsion; 
 
 
       or,
 ii) for composition (b):
 mixing an aqueous solution of Kraft lignin and the base with an aqueous dispersion of the wax. 
 
 
     
     
         14 . The method of  claim 13 , wherein, for (i), the method further comprises maintaining the emulsion at a temperature above 85° C. or above 25° C. 
     
     
         15 . The method of  claim 13 , wherein, for (ii), the mixing is performed immediately before adding to a gypsum slurry or in combination with a gypsum slurry.